In 2002, NASA GRC was
selected by NASA Headquarters Office of
Space Science, Solar System Exploration
Division, under a competitive NRA to develop
high-power electric propulsion for nuclear
systems. In 2003, the propulsion
technologies unique to nuclear power systems
were transferred to NASA's technology
initiative under
Project Prometheus.

The NASA GRC proposal, High Power
Electric Propulsion (HiPEP) is focused on
the development of a 20-50 kW class ion
thruster with a specific impulse of
6000-9000 seconds, and a propellant
throughput capability exceeding 100 kg/kW
– with the intent of bringing the thruster
to TRL 4-5 within 2 years. The HiPEP team is
comprised of
GRC,
Colorado State University,
University of Michigan, and
University of Wisconsin.

The HiPEP project in June 2003 completed its Phase 1 6- month study effort.
During Phase 1: the thruster conceptual design was completed; testing of components were
initiated including discharge, neutralizer,
and subscale ion optics, and; preliminary
full-scale laboratory thruster fabrication
is nearing completion. An assessment of the
thruster design approach for the
JIMO
mission was also conducted, indicating it
meets all potential requirements.

The thruster approach selected was
established based on the critical
requirement – life time – which
influences all thruster design attributes.
All other performance requirements for the
thruster have been previously demonstrated
in the last 30+ years at NASA GRC using
various fidelity thruster hardware (for
example, >200 kW operation at > 7,000
seconds specific impulse, in 1967).

The basic design of the thruster is
rectangular with an ion extraction plane
that will measure approximately 41x 91 cm,
which significantly minimizes the current
density relative to the SOA. The thruster
will generate the discharge plasma via
microwave driven electron cyclotron
resonance, and extract the beam using
pyrolytic graphite grids. Even though the
thruster will be designed to operate up to
50 kW, it will be derated to operate at
approximately 25 kW. This derated approach
greatly improves the likelihood of success
and enhances its growth potential for
future, higher power applications.

Laboratory model thrusters in Phase 2
will be used as a test bed for evaluating
the discharge and ion optics component
technologies. Selection of a final design
will be completed by the end of Year 1 of
Phase 2. Subsequent thrusters will be
manufactured by Aerojet which will then
undergo detailed performance testing, and a
1000 hour wear test.